The invention relates to an apparatus for weighing the hook load of a crane, wherein different measurement accuracies can be set at the apparatus, comprising at least one measurement device, at least one retaining pin, and at least one coupling section, wherein the apparatus is provided between a boom and the hook of a crane, wherein the retaining pin and/or the measurement device can be positioned at at least two different positions at the coupling section, and wherein the positions are in particular horizontally spaced apart from one another.
It is prior art with cranes, and in particular with lattice mast cranes, to carry out the load weighing, that is the weighing of the weight of a load attached to the crane hook or hook load, via the measurement of the guying forces in the guying of the corresponding crane. The weight of the hook load is then calculated from the determined guying forces while taking account of the known boom geometry or crane geometry. It is furthermore known with telescopic cranes to detect the forces occurring in the luffing ram and likewise to calculate the load at the hook via the known geometry of the telescopic crane. Systems are furthermore known that e.g. determine the forces occurring at the cable lines of the crane e.g. by means of a load cell and that measure the load applied to the hook while taking account of the reeving of the crane.
It is problematic with the apparatus known from the prior art that the load measurement is carried out with the same apparatus independently of whether particularly large or particularly small weights or loads are just attached to the crane. It can occur in this process that the sensor used in the apparatus is used for determining a large range of weights, with said sensor not having sufficient measurement accuracy for both large weights and small weights simultaneously. This is linked to the fact that known measurement sensors typically only have a limited measurement range and can correspondingly deliver less accurate values on the exceeding thereof.